You need to check with a dealer. The last message hinted at recall notice on those caps. I did check my parts manual for the P216s, however my manual only goes to I/11313. You engine is diffinetly newer. In my manual they list 11 different caps w/dipsticks and 3 different tubes, all of which slide into a rubber seal at the crankcase. If you want to change tubes and caps you'll need to consult a parts manual that covers your specification number. The specification number designates all the different options available for each engine. The H in your spec number designates that engine has had 8 major manufacturing changes.
The manual also list an o-ring that goes on the cap. Maybe try a new o-ring or one that has a slightly large diameter. Hope this helps.

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Clay Walsten
ET III
Developed Regional Parks
City of San Diego